A Rankine cycle includes: a refrigerant pump adapted to circulate a refrigerant; a waste heat collector adapted to collect the waste heat of an engine with the refrigerant; an expander adapted to convert the waste heat collected with the refrigerant into the driving force by expanding the refrigerant; and a condenser adapted to condense the refrigerant expanded by the expander. The driving force retrieved by the expander is transmitted to the output shaft of the engine and a power generator via belts and the like.
JP2005-313878A discloses that a refrigerant pump is driven before the operation of the expander of the Rankine cycle is initiated (hereinafter referred to as “preliminary driving”), in order to properly adjust the distribution of the refrigerant (including lubricant component) in the Rankine cycle.